Quartz bulb



Patented Mar. 24,, .1931

times) sTAT sr TENT OFFICE ALBERT 3'. roErsINGEE, IQF PRovInEncE, nHonE ISLAND, nssrenort r GENERAL FIRE .EXTINGUISHERCOMPANY, 0E PROVIDENCE, RHODE ISLAND, A CORPORATION, on

DELAWARE QUARTZ BULB Application filed November 30, 1929. Serial no. 4103511 had air cells, or voids in their walls,'m ore or less attenuated, and appearingi'as ajmynad of long straight striae of exceedingly small' cross section; This follows from the fact} that wlieneither quartz sand or'quartz crystals are fused the resulting molten mass has a large number of cells, Containing either a gas or a liquid, which do not glve up their contents because while the quartz maybe brought to a viscous state it can not be made liquid enough for the contents of these cells to escapeby bulbing to the surface. Accordingly the cells remain in the molten mass and ifthis be merely drawn straight out to form a tube as has been the practice, the same cells will appear in the wall of the tube, albeit they are necessarily stretched by the pulling and made smaller in cross section. Likewise in bulbs made from such tubes, the walls thereof will also be characterized by the same striae as were present in the tube. 7

These cellular striae, whether empty or filled with air or other fluid, are elements of weakness in the'finished bulb and are particularly undesirable in bulbs subjected to internal pressure because ithas been observed that on the rupture of such bulbs so used the plane of cleavage most frequently follows one or more of these elongated voids. Since the latter have heretofore extendedlongitudinally: of the bulb, in direction common with its recognized weakest dimension, these cells or voids in effect constitute incipient planes or lines of fracture and thereby materially weaken the bulb. I This effect is so pronounced in bulbs made from quartz sand, where such cells are much greater in number, that such bulbs can not be relied upon where any great internalpressures are employed; For such work it has been; deemed necessary, from the quartz crystals has a less number of cells or voids thanis present in a molten; mass of fused quartz sand, and these can be largely eliminated bycarrying out the initial fusing in an electric furnace -in which a vacuumis created, and-then subsequently reheatin the mass and subjectingit to pressure to rive; out the voids. But thisworking and rework ing of the material is expensive and ifprac- 'ticed in the production of bulbs for coihmer-- cial use would render the cost of'ythelatter entirely prohibitive" Consequently, as "a practical matter; quartz crystals most --free from cells have beencarefully' selected and" I desired.- e

of weakness'ior planes of fracture not to be lhe p'res ent invention resides in a bulb which has its' 'cells disposed in lines more or less transverse to I its axis,;and preferably of c ever-changing direction. Such bulbs can be produced by drawing out the quartz in the roan-sf a tube andtwisting'thetube about as axis as it is'being ,drawn out orfwhen it has been'drawn out, or the quartz cambe drawn out as a solid threadorribbon and wrapped about a mandrel, each convolution adhering to: thefn'ex't and thereby producing a finished tubewhose cells are arranged jhelicalfly'about its axis. A bulb made from quartz so handled will'lhave the cells in its wall similarly disposed about its axis, and its resisting'powe r to internal pressure will in consequence be greatly increased. In fact', bulb s having theircells so disposed are so much stronger thanbulbs heretofore made,-tha t the opaque" form of quartz the safnd quartz-can now be used for bulbs where before only, bulbs made from thechoicest of crystals were deemed safe. A'nd'bulbs can be madeof quartz crystals as they come, twithout' any selection thereof;

whatever: I As'aresult the bulbof the invention isnot only muchfstronger and more re-- liable but is easier to produce and less expensive.

Figure 1 of the drawings shows a bulb embodying the features of this invention, the lines representative of the cells or voids being, for clearness, necessarily larger than the striae which they represent; and V Figure 2 illustrates an automatic sprinkler head employing such a bulb as a frangible strut.

The bulb A is made of quartz which initial ly may have been in the form of sand or rystals. The cells B in the wall of the bulb are disposed helically about the axis of the bulb in ever changing directions. This arrangement of the striae overcomes the danger of premature rupture heretofore present in bulbs having cells extending longitudinally of the wall in directions parallel to the axis of the bulb. In consequence, bulbs like that illustrated can be relied upon to resist greater internal pressures and to act with more uniformity in their performance, because the improved disposition of the cells gives added strength especially when the bulb is called upon to withstand internal pressure. p

lsuch bulbs areparticular ly' adapted for useas the frangible strut of an automatic sprinkler head. In such use the bulb contains a charge which upon rise of tempera ture to a predetermined degree generates an internal pressure sufficient to completely shatter the bulb; The charged bulb is mounted between a yoke G and a glass button D that closes the opening of a diaphragm E secured betweenthe yoke-ring F and the base G of the sprinkler. The latter is threaded so as to be screwed into a conduit of a sprinkler system, the conduitnormally containing air or a fire extinguishing fluidunder pressure. The head isassembled by first securing the diaphragin in place, the button is then seated within its hole of the diaphragmand a suitablebearing ring on plate H is placed in the hollow of the button to receiveone end of the bulbA. The other end of the latter is then engaged by another bearing ring I attached rotatably to an adjusting screw J which screws through the top of theyoke. This screw is then tightened, exerting pressure on the bulb and thus upon the button causing the latter to seat firmly on the diaphragm. When sufficient pressure has thus been established the screw is pinned to the yoke, the deflector K added and the end of the screw riveted over to hold the deflector in place. 7

It will thus be seen that inthis use of the bulb it is always under compressive stress even more important that bulbs beable to resist the internal pressure generated by the heatingof'its charge, until that degree of temperature is reached at which the shattering of the bulb is desired. If it should split or partially fracture at some lower temperature, thereby permitting its charge to escape, the shattering pressure never could be realized and consequently the sprinkler would not open as planned. This, of course, would be fatal. to the protective purpose of the device, and hence the importance of the present invention is apparent, for by eliminating the heretofore dangerous lines'of cleavage, extending longitudinally of the bulb, and providing a bulb with its cellular striw disposed more or less transversely about its axis the bulb is well able to resist the rising internal pressure until the shattering degree is reached. Y

-I claim: H

1. A quartz bulb having its cellular striw disposed within its wall so as to intersect a plane containing the axis of the bulb; 2. A quartz bulb having its cellular striae disposed within its wall helically with respect to the longitudinal axis ofthe bulb. ,Signed'at Providence, Rhode Island, this 29th day of November, 1929. I

ALBERT J. LOEPSINGER- 

